Dilators of various types have been used in the past and are still used today for an assortment of purposes.
Catheters account for a large amount of the instruments used for dilation today. Balloon catheters are commonly used in angiography, angioplasty, angioocclusion, endoscopy, and cervix and uterus examination and surgical procedures. These balloon catheters are simply catheters having a distal balloon that can be inflated at a target site, i.e., a blood vessel. Such catheters are described in U.S. Pat. Nos. 3,882,852, 4,684,363, 5,171,221, and 5,188,630.
Trocar catheters are generally used in emergency situations, and, in particular, are used for insertion into the chest or stomach wall of a patient for withdrawal of fluid within a body cavity, rather than for dilation of body tissue. Such catheters are described in U.S. Pat. No. 3,613,684.
Balloon and trocar catheters, while useful in many surgical procedures, are generally not particularly suited to neurosurgery. Nerve cells or neurons receive, conduct and transmit signals. Communication depends upon an electrical disturbance produced in one part of the cell which spreads to other parts of the cell, and neurons are woven together to form circuits of great complexity. The nerve bundles in the brain are surrounded by connective or supporting tissue called glial cells. The nerve tissue is generally stronger and more resistant to rupture than connective tissue, but care must still be exercised with respect to nerve tissue to avoid damage thereto. In the past, to access an internal section of the brain, it was necessary to cut an opening in the brain with a scalpel. In the process of creating a hole large enough to permit access to a tumor, an extraordinary amount of nerve tissue had to be severed, thereby creating permanent injury to the brain.
U.S. Pat. No. 4,312,353 describes a method for using a catheter to permit surgical operations without the use of a scalpel to cut away tissue. The catheter described is a stylette surrounded by an inflatable sac. Upon insertion into the brain, the sac may be inflated to push aside the connective tissue creating an opening for surgery. The main problem with this catheter is that it is unable to determine when the catheter has been inserted to the desired target prior to inflating the expandable sac. This can result in unnecessary damage to neurons and connective tissue. Further, there is also no method to remove fluid which may fill and block the newly created opening.
A need therefore exists for a dilator which can verify entry into a cerebral ventricle, cystic tumor, abscess, hematoma or any fluid filled cavity. A further need exists for a dilator which can remove and drain fluid which may block the newly created opening in brain connective tissue, thereby creating a bloodless tract through which surgery may be performed. The foregoing and other needs are satisfied by the present invention and will be apparent from the description of the invention provided herein.